a. Field
This invention relates generally to a method and system for the generation of steam from dirty water and produced water. The system and method in a preferred embodiment is a Once Through Steam Generation (OTSG) system, apparatus and method an can be a Zero Liquid Discharge (ZLD) system, apparatus and method. The steam product can be used in any steam application but is particularly well suited for Steam Assist Gravity Drain (SAGD) heavy oil applications.
b. Background Art
Once Through Steam Generators (OTSG) are the most common steam generation systems used in SAGD and Cyclic Steam Stimulation (CSS) heavy oil recovery. The heavy oil industry today uses 2 to 4 barrels of water (turned into steam) for every barrel of oil it produces. The oil and gas industry currently utilizes extensive water treatment technologies at the well site to clean its process water before making steam typically in an OTSG. It is a common comment that modern SAGD sites are really a large and expensive water treatment plant attached to a small well pad. The water treatment plant and process currently used in conventional OTSG requires extensive labor and large amounts of expendable chemicals to operate. During normal operations these water treatment plants produce a significant waste stream of lime sludge and other byproducts that must be disposed of Due to the operational expense and capital required to build ever more complete water treatment plants the norm in the oil industry is to limit the steam quality from 70 to 80% in the OTSG. In other words 20 to 30% of the liquid input or feed water stays in a liquid state and is not converted to steam. This practice helps to limit the deposits that will build up inside the OTSG which will eventually disable its operation. To produce a higher quality steam, the water would first have to be treated to a higher purity level adding additional expense and complexity to an already too large and too complex water treatment system. Unfortunately the practice of low quality OTSG steam production is energy inefficient since the spent process water, or blow down, wastes most of its energy without recovering any oil product. This practice produces excessive greenhouse gasses (GHG) from the wasted energy and another waste stream from the OTSG which is the blow down fluid. The amount of blow down produced is significant. The blow down waste contains many contaminated solids such as CAO3 and MGO3. This blow down must be disposed of in deep wells or again run through some very expensive and complex processes to reclaim the valuable water content. The invention taught in this patent eliminates the need for clean water and all its expense. It also eliminates all waste streams including blow down and can in an embodiment be a Zero Liquid Discharge system, a Zero GHG System and a Zero Waste System.